I don't like that #Firefox has "Developer Edition" it only increases the bar for people to experiment.
For me, browsers have been the last bastion of hackability in the modern app ecosystem. I understand why Google #Chrome and Apple #Safari don't want people to make all kinds of extensions.
Firefox is the underdog at the moment, they should:
Aim to make the out-of-the-box experience familiar,
Be customizable so people can build wild ideas like Arc Browser is doing as an extension.
